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Need help putting together Greenhouse hydronic system

panga Member Posts: 2
I am trying to put together a greenhouse radiant heat system, I have done the heat loss calls and know how many BTU system I need. I need help with the deign from there. The system will need to heat 3 greenhouses all different sizes but ran off same boiler. I'd like to keep it as simple as possible. I don't think separate zone control is necessary, as the greenhouses will be kept at the same temperatures, and all ran at the same time, the amount of ex in each house will obviously very based on square footage. The system will have 3/4" PEX suspended under benches in the greenhouses. I have used systems like this sold by farm trek in the past and they worked well. Concrete slab is out of the budget.

-Central outdoor on demand water heater for heat source
-hopefully one pump to distribute hotter
-manifold at each greenhouse

I have put these systems together in the past using the premade "boiler integration panels" and lex loop quick connect manifolds, which made it easy. This time I am not sure how to plumb the system with a manifold at each of the greenhouses, Should it be plumbed inline, boiler to manifold 1, then to manifold 2, then manifold 3? Please advise, I know I am an amateur, but this has to be a DIY project due to budget. Thanks for the help.


  • Jamie Hall
    Jamie Hall Member Posts: 18,964
    I'm concerned about using an on-demand water heater as your heat source. They aren't intended for continuous duty heating work. I would suggest a boiler made for the purpose. Granted, they are more expensive, but they also last a lot longer.

    I would not plumb it in line -- if you do, unless I seriously misunderstand what you are describing, the water temperature in the three manifolds will not be the same, making control much more difficult than it needs to be. Rather, I would have all three manifolds in parallel, and use flow balancing valves to further get the loops flowing at the temperatures and temperature drops you need.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • panga
    panga Member Posts: 2
    Ok great thanks for the advice. Do you have a boiler recommendation? Propane & inexpensive as possible with out being crap. The system will likely run 12hrs a day for 3 months a year. Thanks again really appreciate it!